Download MINITAB_Basics - Penn State Department of Statistics

Department of Statistics
Penn State University
Introduction to Minitab 12 for Windows
IBM/DOS Public Labs
Minitab for Windows is available for student use at all public computer labs at the
University Park campus. Students need an access account user ID and
password to use any computer in the labs. In this document all commands will be
carried out with pull-down menus and the mouse in an exclusively Windows
environment.
Starting Minitab
Once you have logged onto a CAC computer, click on the Start button in the
bottom left-hand corner of the screen. A menu will appear which includes
Statistics and Spreadsheets. Move the mouse to this selection and click on
Minitab 12 from the sub-menu that appears. This will activate the software.
Figure 1: Minitab for Windows
Figure 1 illustrates how Minitab looks when you first begin the program. Initially,
the Session window and the Data window are open. The title bar of the active
window is blue, and the other window has a gray title bar. The outer-most or
background window contains pull-down menus for statistical analyses, and short
cut buttons. If you position the mouse over any of the short cut buttons without
clicking, a description of the button will appear.
Worksheet window: The Worksheet window is where you enter the data to
be analyzed. The data for each variable is stored in a different column. At
the top of each column is a blank cell for specifying the name of the
variable. A variable may be referred to by its name or column location (c1
for column 1, c2 for column 2, etc.) (If the Data window is not visible on
the screen, select Data from the Window pull-down menu. This will
activate the Data window.)
Session window: In general, the Session window is where Minitab will print
the results of an analysis. Minitab also prints the commands that
generated the results in the session window, too, but don't worry about the
commands. You will use pull-down menus to tell Minitab what to do. (If
the Session window is not opened, select Session from the Window
menu to open the window.)
You may edit the output in the Session window, delete lines or add lines,
much as you would in a word processor. This feature can be very useful
for the preparation of assignments.
History window: This window lists all the commands that have been
entered during the current Minitab Session, but without the output
generated by those commands. The history window may be accessed by
selecting History from the Window menu at the top of the screen.
Info window: This window lists information about the active worksheet (i.e.
the data currently showing in the Data window). This window is also
accessed from the Window menu.
Entering Data
To enter data, you have to activate a Worksheet window by clicking once on the
Worksheet window's title bar. The Worksheet window is active when the title bar
turns blue. Use your mouse, the keypad, and the carriage return to enter the
following data into columns C1 and C2. The data represent the average
temperatures for Atlanta and New York for the twelve months of the year.
C1
C2
C3
Month Atlanta New York
1
1
42
32
2
2
45
33
3
3
51
41
4
4
61
52
5
5
69
62
6
6
76
72
7
7
78
77
8
8
78
75
9
9
72
68
10
10
62
58
11
11
51
47
12
12
44
35
The space above the first row is reserved for variable names. If you haven't
already done so, name the first column "Month", the second column "Atlanta",
and the third column "New York." If you choose not to specify variable names,
you can refer to the variables during analysis by their column names, namely C1,
C2, etc.
Should you mistakenly enter an incorrect value, editing data is simple. Simply
move to the data cell, by clicking once on the desired cell, and type in the
corrected value. The pull-down Edit menu offers some other editing functions
which may be of interest.
Analyzing Data
Once you have entered the data, you can analyze the data graphically or
numerically. In general, all of the graphical analyses available in Minitab are
under the Graph menu, and all of the numerical analyses available in Minitab are
under the Stat menu. Also, in general, the results of numerical analyses appear
in the Session window, while graphical results appear in a separate graph
window.
As an example of a numerical analysis, calculate the basic descriptive
statistics (n, mean, minimum, range, etc.) for Atlanta's average monthly
temperatures:
Select Stat.
Select Basic Statistics.
Select Display Descriptive Statistics...
The Display Descriptive Statistics Pop-Up Window will appear. In the left
box, click once on the variable you want analyzed ("Atlanta"). Click once
on the Select button. The column name (or variable name) will appear in
the box labeled Variables.
5. Select OK. The output will appear in the Session window.
1.
2.
3.
4.
The following output should appear:
Descriptive Statistics
Variable
SE Mean
Atlanta
13.80
Variable
Atlanta
N
Mean
Median
TrMean
12
60.75
61.50
60.90
Minimum
42.00
Maximum
78.00
Q1
46.50
Q3
75.00
StDev
3.98
Now, as an example of a graphical analysis, create a boxplot of New York's
average monthly temperatures:
1. Select Graph.
2. Select Boxplot....
3. The Boxplot Pop-Up Window will appear. In the left box, click once on the
variable you want analyzed ("NewYork"). Click once on the Select button.
The column name (or variable name) will appear under the Y in the box
labeled Graph Variables.
4. Select OK. A new graph window, which contains the boxplot, will appear.
Saving Your Work
Once you've entered data and performed your analyses, you may want to save
your work for later use. You can either save just your data ("the worksheet") or
you can save your data and your output ("your project").
To save just your data:
1. Select File.
2. Select Save Current Worksheet As...
3. The Save Worksheet As Pop-Up window will appear. If it does not say
"31/2 Floppy (A:)" in the Save in: box, click on the yellow folder button
with an arrow to the right of the Save in: box to find the A: drive.
4. Type the desired file name in the File name: box.
5. Select Save. Minitab will save the file with your desired name and an
*.mtw extension.
To save your data and your work:
1. Select File.
2. Select Save Project As...
3. The Save Project As Pop-Up window will appear. If it does not say "31/2
Floppy (A:)" in the Save in: box, click on the yellow folder button with an
arrow to the right of the Save in: box to find the A: drive.
4. Type the desired project name in the File name: box.
Select Save. Minitab will save the project with your desired name and an
*.mpj extension.
Opening Your Previous Work
Opening a worksheet or project works similarly as saving a worksheet or project.
To open a worksheet (*.mtw):
1. Select File.
2. Select Open Worksheet...
3. The Open Worksheet Pop-Up window will appear. Using the the yellow
folder button with an arrow to the right of the Look in: box, find the drive
that contains the desired worksheet.
4. Select the desired file so its name appears in the File name: box.
5. Select Open. Minitab will open the desired worksheet.
To open a project:
1. Select File.
2. Select Open Project...
3. The Open Project Pop-Up window will appear. Using the the yellow folder
button with an arrow to the right of the Look in: box, find the drive that
contains the desired project.
4. Select the desired file so its name appears in the File name: box.
5. elect Open. Minitab will open the desired project.
Using Help
Minitab for Windows has a comprehensive help database with detailed
information on all the commands and topics. There are two ways of accessing
help. When you want to learn more about Minitab for Windows or a specific topic,
go to the Help menu at the top of the screen and select Contents. Clicking on
the ? button on the tool bar will also call up the help window.
If you are using a specific command and are confused by any of the options
listed in the dialog box for that command, simply click the Help button within the
dialog box. This will provide you with detailed explanations of the available
options for the command you are using. You may also print information from the
Help database. Please print only those pages which are of use to you since the
printers are shared by everyone.
Printing
Printing graphs, data or session windows can be done at any stage of your
Minitab session. To print any window:
1. If it is not already, activate the window you wish to print by clicking
anywhere on the window. (The window is activated when the bar is blue;
it is not activated when the bar is gray.)
2. Select File.
3. Select Print Window.
4. Select OK.
The contents of your window will print out at the default printer in the lab in which
you are working.
Exiting Minitab
Before exiting Minitab, be sure that you have saved your worksheets and/or
project. Then to exit Minitab:
1. Select File.
2. Select Exit.
Minitab Cheat Sheet for Descriptive Statistics
All of the following procedures assume you have already entered your data correctly into
one (or more) of the columns in the Minitab Data Window.
To produce a one-way distribution table for categorical data:
1.
2.
3.
4.
Select Stat.
Select Tables.
Select Tally.
The Tally Pop-Up Window will appear. In the left box, click once on the variable
you want analyzed. Click once on the Select button. The column name (or
variable name) will appear in the box labeled Variables.
5. Under Display, click on the appropriate box(es) to select the statistics that you
want calculated. Counts, Percents, and Cumulative Percents will give you a
complete distribution table as described in your text.
6. Select OK. The output will appear in the Session Window.
To produce a two-way distribution table for categorical data:
1.
2.
3.
4.
Select Stat.
Select Tables.
Select Cross Tabulation.
The Cross Tabulation Pop-Up Window will appear. In the left box, click once on
the variable you want to treat as the row variable. Click once on the Select button.
The column name (or variable name) will appear in the box labeled Classification
Variables. Then, in the left box, click once on the variable you want to treat as the
column variable. Click once on the Select button. The column name (or variable
name) will appear in the box labeled Variables.
5. Under Display, click on the appropriate box(es) to select the statistics that you
want calculated. Counts reports the number of units falling into each cell. Total
Percents reports the percent of all units falling into each cell (number in cell
divided by grand total). Row Percents reports percent in row falling into each
level of the column variable (number in cell divided by row total). Column
Percents reports percent in column falling into each level of the row variable
(number in cell divided by column total).
6. Select OK. The output will appear in the Session Window.
To create a stem-and-leaf plot:
1.
2.
3.
4.
Select Graph.
Select Character Graphs.
Select Stem-and-Leaf...
The Stem-and-Leaf Pop-Up Window will appear. In the left box, click once on
the variable you want analyzed. Click once on the Select button. The column
name (or variable name) will appear in the box labeled Variables.
5. Select OK. The output will appear in the Session Window.
To create a dot plot:
1.
2.
3.
4.
Select Graph.
Select Character Graphs.
Select Dotplot...
The Dotplot Pop-Up Window will appear. In the left box, click once on the
variable you want analyzed. Click once on the Select button. The column name
(or variable name) will appear in the box labeled Variables.
5. If you want to create dot plot for more than one variable simultaneously, click on
the box labeled Same Scale for all variables.
6. Select OK. The output will appear in the Session Window.
To create a histogram:
1. Select Graph.
2. Select Histogram.
3. The Histogram Pop-Up Window will appear. In the left box, click once on the
variable you want analyzed. Click once on the Select button. The column name
(or variable name) will appear under the X in the box labeled Graph Variables. (If
you would like a relative frequency histogram rather than the default frequency
histogram, click on Options. Click on Percent. Select OK.)
4. Select OK. A new graph window, which contains the histogram, will appear.
To create a scatter plot:
1. Select Graph.
2. Select Plot.
3. The Plot Pop-Up Window will appear. In the left box, click once on the Y
variable you want analyzed. Click once on the Select button. The column name
(or variable name) will appear under the Y in the box labeled Graph Variables. In
the left box, click once on the X variable you want analyzed. Click once on the
Select button. The column name (or variable name) will appear under the X in the
box labeled Graph Variables.
Select OK. A new graph window, which contains the scatter plot, will appear.
To calculate descriptive statistics:
1.
2.
3.
4.
Select Stat.
Select Basic Statistics.
Select Display Descriptive Statistics.
The Display Descriptive Statistics Pop-Up Window will appear. In the left box,
click once on the variable you want analyzed. Click once on the Select button.
The column name (or variable name) will appear in the box labeled Variables.
5. Select OK. The output will appear in the Session Window.
To create a boxplot:
1. Select Graph
2. Select Boxplot.
3. The Boxplot Pop-Up Window will appear. In the left box, click once on the
variable you want analyzed. Click once on the Select button. The column name
(or variable name) will appear under the Y in the box labeled Graph Variables.
4. Select OK. A new graph window, which contains the boxplot, will appear.
Minitab Quick Reference
Describing and analyzing categorical (qualitative)
data
To produce tally for one categorical variable:
1. Stat>Tables>Tally.
2. Select the variable you want to summarize by double clicking it
3. Under Display, click on the appropriate box(es) to select the
statistics that you want calculated
4. Select OK. The output will appear in the session window.
To produce contingency table (cross tabulation) for two categorical
variables:
1. Stat>Tables>Cross Tabulation
2. Select the variables you want to summarize by double clicking
on them (if one variable can be designated as explanatory and
the other response, it is customary to define the rows using the
explanatory variable and the columns using the response
variable)
3. Under Display, click on the appropriate box(es) to select the
statistics that you want calculated
4. Select OK. The output will appear in the session window.
To test whether two categorical variables are independent:
1. Stat>Tables>Chi-Square Test
2. Select the variables you want analyzed by double clicking on
them
3. Select OK
To create a bar graph for a categorical variable:
1. Graph>Chart
2. Specify the categorical variable in the X text for Graph 1
3. Select OK.
If you want to show subgroups within the groups on the x-axis, click
on options and select clustering or stacking. Enter the categorical
variable for the subgroups. Clustering shows each subgroup as a
separate bar. Stacking shows subgroups as blocks stacked on top of
each other.
To create a pie chart for a categorical variable:
1. Graph > Pie Chart
2. Specify the categorical variable in the Chart data in text box
3. Select OK.
To make inferences (test and confidence interval) about one
population proportion:
1. Stat > Basic Statistics > 1 Proportion
2. Dialog box items :
a. Samples in columns: Enter the column(s) containing the
sample data. Each cell of these columns must be one of two
possible values and correspond to one item or subject. The
possible values in the columns must be identical if you
enter multiple columns.
b. Summarized data: You can enter summary data if they are
in that form.
3. Click on Options … In the Confidence Level text box, type
your desired confidence level. In the Test proportion text box,
specify the value of the proportion in the null hypothesis. In
Alternative text box, select the desired alternative hypothesis
from : not equal, less than, greater than.
4. Click on the box before Use test and interval based on normal
distribution if you want to use the normal approximation to
Binomial distribution.
5. Select OK.
6. Select OK.
To make inferences (test and confidence interval) about two
independent population proportions:
1. Stat > Basic Statistics > 2 Proportions
2. Dialog box items:
a. Sample in one column: Choose if you have entered raw
data into a single column with a second column of
subscripts identifying the sample.
b. Samples in different columns: Choose if you have entered
raw data into single columns for each sample.
c. Summarized data: Choose if you have summary values for
the number of trials and successes.
3. Click on Options … In the Confidence Level text box, type your
desired confidence level. In the Test difference text box, specify
the value of the difference in the null hypothesis. In Alternative
text box, select the desired alternative hypothesis from: not equal,
less than, greater than.
4. Select OK.
5. Select OK.
Describing and analyzing quantitative data
To calculate descriptive statistics:
1. Stat > Basic Statistics > Display Descriptive Statistics
2. Specify the quantitative variable in the Variable text box
3. Select OK.
To create a dot plot:
1. Graph > Dotplot
2. Double click on the quantitative variable you want to plot
3. By default, the radio button in front of No Grouping is selected
and that will create one dotplot.
4. If you want to create a dot plot for different groups and your
groups are in different columns, then click on the radio button in
front of "Each column constitutes a group." If you want to create
a dot plot for different groups and your group variable is in one
column and the data in another column, click on the radio button
in front of By Variable. Then, click on the box after By
Variable. In the left box, click once on your grouping variable.
Click on the Select button. The column name (or variable name)
will appear in the box labeled By Variable.
5. Select OK. A new graph window, which contains the dotplot(s),
will appear.
To create a histogram:
1. Graph > Histogram
2. Double click on the quantitative variable you want analyzed. (If
you would like a relative frequency histogram rather than the
default frequency histogram, click on Options. Click on Percent.
Select OK.)
3. Select OK. A new graph window, which contains the histogram,
will appear.
To create a boxplot:
1. Graph > Boxplot
2. Double click on the quantitative variable you want analyzed. The
column name (or variable name) will appear under the Y in the
box labeled Graph Variables. If you would like to create a graph
that shows side-by-side boxplots, similarly select a categorical
variable to enter under the X in the box labeled Graph Variables.
3. Select OK. A new graph window, which contains the boxplot(s),
will appear.
To create a stem-and-leaf diagram:
1. Graph > Stem-and-leaf
2. Specify the quantitative variable you want analyzed in the
Variables text box.
3. Select OK. The output will appear in the Session Window.
To check whether the data follows a normal distribution:
1. Graph > Probability Plot
2. Specify the variable you want to check for normality
3. Select OK
To make inferences (test and confidence interval) about
the difference
in the means of two independent populations
1. Stat > Basic Statistics > 2-sample t
2. Dialog box items:
a. Samples in one column: Choose if the sample data are in a
single column, differentiated by subscript values (group
codes) in a second column.
b. Samples in different columns: Choose if the data of the two
samples are in separate columns.
c. Assume equal variances: Check to assume that the
populations have equal variances. The default is to assume
unequal variances.
3. Click on Options … In the Confidence Level text box, type
your desired confidence level. In the Test difference text box,
specify the value of the difference in the null hypothesis. In
Alternative text box, select the desired alternative hypothesis
from: not equal, less than, greater than.
4. Select OK.
5. Select OK.
To make inferences (test and confidence interval) about the
difference in the means of two dependent populations
1. Stat > Basic Statistics > Paired t
2. Click in the First sample textbox and specify the data from the
first population. Click in the Second sample textbox and specify
the data from the second population.
3. Click on Options … In the Confidence Level text box, type
your desired confidence level. In the Test mean text box,
specify the value of the difference in the null hypothesis. In
Alternative text box, select the desired alternative hypothesis
from: not equal, less than, greater than.
4. Select OK.
5. Select OK.
To make inferences (test and confidence interval) about the means of
three or more independent populations
1. Stat > ANOVA > Oneway
2. Click in the column containing the response in the Response text
box and the column containing the factor levels in the Factor
text box.
3. Select OK.
To plot two quantitative variables (scatterplot)
1. Graph > Plot
2. Click in the Y textbox and specify the variable you want to put in
the vertical axis. Click in the X textbox and specify the variable
you want to put in the horizontal axis.
3. Select OK.
To plot two quantitative variables with fitted line
1. Stat > Regression > Fitted Line Plot
2. Click in the Response textbox and specify the response variable.
Click in the Predictors textbox and specify the variable you
want to put in the predictor variable.
3. Choose linear if you want to fit a straight line.
4. Select OK.
To analyze relationship between two or more variables
1. Stat > Regression > Regression
2. Click in the Response textbox and specify the response variable.
Click in the Predictors textbox and specify the explanatory
variable(s).
3. Select OK.
To find the correlation coefficient between two variables
1. Stat > Basic Statistics > Correlation
2. Click in the Variables textbox and specify the variables.
3. Select OK.
Calculations
To perform calculations
1.
2.
3.
4.
Calc > Calculator
Name the variable you want to Store the results
Specify the expression
Select OK
To make patterned text data
1. Calc > Make Patterned Data > Text values
2. Type the name you want to call the column in the Stored
patterned data in textbox
3. Type the base pattern for the text
4. Enter the number of times you want to repeat each text value
within the sequence in the List each value textbox and enter the
number of times you want to repeat the entire sequence in the
List the whole sequence textbox
5. Select OK
To obtain a simple random sample
1. Calc > Random Data> Sample from Columns
2. Indicate the number of rows you want to sample from which
columns and where to store the data
3. Check the box sample with replacement if that is what you
want. The default is sample without replacement
4. Select OK
To obtain a random sample from a Bernoulli distribution
1.
2.
3.
4.
5.
Calc > Random Data> Bernoulli
Indicate the number of rows of random data you want to generate
Specify storage column(s) for the generated values
Specify the probability of success
Select OK
To obtain probability distributions
1. Calc > Probability Distributions > then select the distribution you
want.
2. Choose Cumulative probability if you want to find the
probability of the random variable has a value less than or equal
to the value you specify. Choose probability density if you want
that for the value you specify. Choose Inverse cumulative
probability if you want to find the value associated with the
cumulative probability you specify. For example, if you specify
the probability as .9, then the Inverse cumulative probability will
give you the 90th percentile.
3. Choose input column or input constant according to the type of
input you have
4. Select OK